Ethylbenzene is used predominantly for the production of styrene monomer obtained through dehydrogenation. Presently much of the ethylbenzene being produced is obtained by alkylation of benzene with ethylene under a variety of alkylation conditions. One type of alkylation process which is conventional is to employ relatively high pressures and temperatures to obtain vapor phase reaction conditions wherein the ethylene and benzene are converted in the presence of catalyst materials. Both single and multiple catalyst bed processes are well known in the art. One problem in the production of ethylbenzene by such mwethods is the production of unwanted by-products which can be very detrimental because some of the by-products may be very difficult, or impossible, to separate from the desired ethylbenzene product. Thus, as an example, the production of xylene in these types of processes is very undesirable since separation of xylene from the ethylbenzene product is very difficult from a processing standpoint. In addition to the requirement that the catalyst employed in such processes be selective to the desired ethylbenzene product it is also desirable to obtain acceptable conversion of the reactants to alkylated products. The ability of different catalyst materials to convert the raw feed materials into products is sometimes referred to as its "activity". Conversion is normally measured as a percentage of the amount of feed materials which will be converted into products during the reaction. The ability of the catalyst to maintain high conversion rates (i.e. retain activity) is also important.
Deactivation of catalysts is one major problem in catalytic alkylation processes, since even if high conversion rates are obtained initially, the failure to maintain good conversion over a long period of time requires expensive catalyst changeouts and/or regeneration procedures. As used herein, the term "stability" refers to the relative activity of the catalyst material as a function of time under the conditions of the stated process.
The use of zeolite type catalysts, of both natural and man-made varieties, in hydrocarbon conversion processing has been known for some time. Aluminosilicate type zeolite catalysts, including those known as ZSM-5 and ZSM-12, for example, have been reported to be suitable for hydrocarbon conversion processes and, in particular, for alkylation of aromatic substrates. One problem with these types of catalysts, however, is that they are subject to rapid deactivation in the presence of even small amounts of water. For example, U.S. Pat. No. 4,197,214 describes a special method for stabilizing these types of crystalline zeolites which is indicated to be necessary if rapid deactivation in the presence of reducing atmospheres (such as those found in alkylation reactors) and high temperatures in the presence of steam is to be avoided.
A distinct type of catalyst material which is synthesized from reaction systems essentially free of aluminum containing reagents and which are therefore either entirely free of framework AlO.sub.4.sup.- tetrahedra or contain no crystalographically significant amounts thereof called "TEA-silicates" are disclosed in U.S. Pat. No. 4,104,294. These TEA-silicate catalysts are reportedly capable of adsorbing at least 28% neopentane which has a kinetic diameter of 6.2 angstroms.
Thus it would be desirable to obtain a process in which conversion of reactants to ethylbenzene can be obtained without production of unwanted xylene by-products and without the necessity of regenerating or replacing the catalytic material employed.